1. Field
Apparatuses and methods consistent with exemplary embodiments relate to a microfluidic device, a light irradiation apparatus, a microfluidic system including the same, and a method for driving the same, and more specifically, to a microfluidic device, a light irradiation apparatus, a microfluidic system including the same, and a method for driving the same, to uniformly heat a fluid sample present in the microfluidic device or smoothly operate a valve.
2. Description of the Related Art
Generally, microfluidic devices used for operations utilizing a small amount of fluid include a chamber to retain a small amount of fluid, a channel through which the fluid flows, and a valve to control fluid flow. A device to perform experiments including biochemical reactions on a small chip is referred to as a biochip, in particular, a device wherein treatment and operations of fluids through a series of steps are performed on one chip is referred to as a lab-on-a-chip.
A driving pressure is required to transfer fluids in a microfluidic device. Capillary pressure or pressure applied by an additional pump is used as driving pressure. Recently, a disc-shaped microfluidic device, called a “Lab CD” or “Lab-on-a-CD” in which chambers and channels are arranged rotates to operate fluids through centrifugal force.
Various valve techniques to control fluid flows in these microfluidic devices are being researched. At present, thermally activated valves using a material to undergo phase-transition from solid to liquid utilizing heat generated by absorbance of electromagnetic waves are being developed.
Operations of thermally activated valves sensitively depend on characteristics of a light source to transfer light energy to a valve material and light energy absorbance efficiency of the valve material.
First, when light energy absorbance efficiency of the valve material is low, light irradiation for a long time and high light source output are disadvantageously required in order to cause phase-transition of the valve material.
When light energy absorbance efficiency of the valve material is high, excessively long light irradiation time makes the valve material excessively hot, thus causing serious deformation of a substrate and biochemical variation of sample fluids adjacent to the valve material due to heat conduction. On the other hand, excessively short light irradiation time provides insufficient phase-transition, thus disadvantageously causing incomplete opening/closing of the valve.
In addition, since related art light sources may have non-uniform light intensity distribution, a portion of the valve may be excessively heated or not heated, although light irradiation time is accurately controlled, thus providing incomplete phase-transition. In particular, for example, these problems may be more serious in valve materials exhibiting poor heat conductivity such as paraffin.
There are differences in light intensity distribution between light sources having identical specifications. For this reason, disadvantageously, microfluidic devices separately using a plurality of light sources have different valve operation characteristics. In addition, upon mass-production of microfluidic devices, it is not easy to impart identical valve operation performance to the microfluidic devices due to the differences in light intensity distribution between light sources provided in the respective microfluidic devices.
For accurate testing of fluid samples accepted in microfluidic devices, the temperature of fluid samples required for the desired tests may be varied.
When the fluid sample temperature is lower than a desired test temperature, heating of the sample fluid is required to elevate the fluid sample temperature to a desired level. In this case, when light intensity distribution of light sources is non-uniform, uniform elevation of the fluid sample temperature is disadvantageously impossible.
In addition, uniform heating of fluid samples is required to perform a variety of tests such as acceleration of reactions of fluid samples with other materials, culturing of cells contained in fluid samples, extraction of nucleic acid through cell lysis, amplification of nucleic acid through polymerase chain reaction (PCR) cycles and the like. Similarly, non-uniform light intensity distribution of light sources disadvantageously makes uniform elevation of fluid sample temperature impossible.